DE3326188A1 - METHOD FOR THE PRODUCTION OF ORGANIC POLYISOCYANATES WITH AT LEAST PARTLY BLOCKED ISOCYANATE GROUPS, THE COMPOUNDS AVAILABLE AFTER THE METHOD AND THE USE THEREOF FOR THE PRODUCTION OF POLYURETHANES, BURNING LACQUES OR WATER POWDERED POLYURATES. -DISPERSIONS - Google Patents

Description

BAYER AKTIENGESELLSCHAFT 5090 Leverkusen, Bayerwerk

Central area

Patents, trademarks and licenses Wr / by-c

Process for the preparation of organic polyisocyanates with at least partially blocked isocyanate groups, the compounds obtainable by the process and their use for the preparation of Polyurethanes, stoving enamels or aqueous polyisocyanate solutions or dispersions

The present invention relates to a new process for the preparation of organic polyisocyanates with at least partially blocked isocyanate groups using cyclic carbonyl compounds as Blocking agents for isocyanate groups, the polyisocyanates obtainable by this process with at least partially blocked isocyanate groups, and their use as reactants for organic Polyhydroxy compounds in the manufacture of polyurethane plastics, of aqueous stoving enamels or of aqueous polyisocyanate solutions or dispersions.

Blocked polyisocyanates, which at elevated temperature with compounds with Zerewitinow-active hydrogen atoms react, are known and are e.g.

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Houben-Weyl, "Methods of Organic Chemistry", volume XIV / 2, pages 61-70 or at Z.W. Wicks, Jr., Progress in Organic Coatings j), 3-28 (1981). Suitable blocking agents for isocyanates are e.g. Phenols, caprolactam, oximes and CH-acidic compounds such as alkyl acetoacetate and dialkyl malonate.

The blocked polyisocyanates of the prior art are suitable in combination with polyfunctional compounds, the Zerewitinow-active hydrogen atoms carry, for the production of thermally curable Plastics, in particular stoving enamels and coatings. You will be mostly in shape of solutions in organic solvents.

For reasons of environmental protection and to save oil-dependent organic solvents, it is now of increasing interest, as are such stoving resins to be able to use in the form of aqueous dispersions or solutions. There has therefore been no lack of attempts to produce water-soluble or water-dispersible blocked polyisocyanates. In general proceeded so that some of the isocyanate groups of Polyisocyanate is irreversibly reacted with compounds that are ionic, potentially ionic or carry non-ionic-hydrophilic groups. The remaining isocyanate groups are with one or more of the above, blocking agents which can easily be split off again at elevated temperature are "capped". This ver

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driving is for example in DE-OS 24 56 469 and EP-OS 12 348 described. As hydrophilic or potentially hydrophilic structural components there are e.g. hydroxycarboxylic acids, Tertiary amines containing hydroxyl groups / hydroxypolyethylene oxides and polyaminosulfonates listed.

The disadvantage of this procedure is that there is always a considerable proportion of the NCO groups used Polyisocyanate is consumed for the reaction with the hydrophilic structural components mentioned. Im blocked Polyisocyanate then this part of the functionality stands for a thermal crosslinking reaction with Zerewitinow-active Reactants carrying hydrogen atoms in the normally used stoving temperatures no longer available. The described hydrophilic blocked polyisocyanates therefore have compared to the corresponding blocked isocyanates, which are applied from organic solution, technical Disadvantages on.

The object of the present invention was to provide blocked polyisocyanates which not only from organic solution, but also from the aqueous phase can be used without modifications to their production would be necessary to the above-described

25 lead technical disadvantages.

This object was achieved by providing the method according to the invention described in more detail below

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or the invention described in more detail below Process products are solved.

The inventive method is based on the surprising Observation that reaction products of certain, described in more detail below, cyclic Dicarbonyl compounds with organic polyisocyanates represent blocked polyisocyanates, which at relatively low stoving temperatures with compounds with Zerewitinow-active hydrogen atoms react and, moreover, in the presence of weak organic ones Bases, such as tertiary amines, are soluble or dispersible in water, it was also surprising that the cyclic dicarbonyl compounds not only relate to aromatic but also to aliphatic isocyanates let add. This is for an application of the adducts in the field of paints and coatings of particular technical importance because of the lightfastness of aliphatic isocyanates.

From the literature only adducts of cyclic dicarbonyl compounds of the type essential to the invention with aromatic monoisocyanates have become known (U. Herzog, H. Reinshagen, Eur. J. Med. Chem. 10 , 323 (1975)). According to these authors, no corresponding adducts could be produced with aliphatic isocyanates. The aim of the cited work was the production of pharmaceuticals and insecticides (see also US Pat. No. 4,073,932 and US Pat. No. 4,123,551). Adducts

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polyfunctional isocyanates and the cyclic isocyanates mentioned Dicarbony compounds have not yet been described. Likewise, there is still nothing about the reactivity of such adducts towards compounds with Zerewitinow-active Hydrogen atoms as well as attempts at such adducts use for applications in the plastics sector, known.

The present invention relates to a method for the preparation of organic polyisocyanates with at least partially blocked isocyanate groups at least partial blocking of the isocyanate groups of organic polyisocyanates with blocking agents for isocyanate groups, characterized in that the blocking agent used is

15 a) the characteristic structural unit

C-O

0
containing cyclic dicarbonyl compounds

and possibly additionally

b) blocking agents known from polyurethane chemistry

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used, wherein the blocking agent a) in, a molar ratio of blocking agent a) to isocyanate groups of the starting polyisocyanate of at least 0.1: 1 corresponding amounts is used, and wherein, In the case of the use of blocking agents b), this before, at the same time with or after the implementation of the starting polyisocyanate with the blocking agent a) reacted with the starting polyisocyanate will.

The present invention also relates to the organic polyisocyanates obtainable by this process with at least partially blocked isocyanate groups.

The invention also relates to the use of the polyisocyanates obtainable by this process at least partially blocked isocyanate groups as reactants for organic polyhydroxyl compounds in the production of polyurethane plastics, especially paints, coatings or sealants based on polyurethane.

The invention also relates to the use of those obtainable by the process according to the invention Polyisocyanates with at least partially blocked isocyanate groups for the production of aqueous stoving enamels, characterized in that the polyisocyanates with aqueous solutions or dispersions of organic compounds with at least

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two isocyanate-reactive groups in the presence of one, the solubility or dispersibility of the polyisocyanates in water ensuring the amount of a base while maintaining an equivalent ratio from blocked isocyanate groups to isocyanate-reactive groups from 0.1: 1 to 1: 1.2 optionally mixed with the use of auxiliaries and additives customary in paint technology.

Finally, the invention also relates to the use the polyisocyanates obtainable by the process according to the invention with at least partially blocked Isocyanate groups for the preparation of aqueous polyisocyanate solutions or dispersions, characterized in that the polyisocyanates in the presence of a, the amount of a base with water which ensures the solubility or dispersibility of the polyisocyanates mixed.

Starting materials for the process according to the invention are any organic polyisocyanates and cyclic ones having the structural unit mentioned above Dicarbonyl compounds.

For the method according to the invention are fundamentally any organic polyisocyanates or any mixtures of organic polyisocyanates are suitable. Examples this includes compounds of the formula

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Q (NCO) _n in which

Q stands for an aromatic, optionally methyl, substituent or a hydrocarbon radical containing methylene bridges with a total of 6 to 15 carbon atoms, an aliphatic hydrocarbon remainder with 4 to 18, preferably 6 to 10 carbon atoms, a cycloaliphatic Hydrocarbon radical with 6 to 15 carbon atoms or a xylylene radical, and

η stands for an integer from 2 to 5.

Typical examples of such suitable according to the invention Polyisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclohexane-1,3- and 1,4-diisocyanate and any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), perhydro-2,4'- and / or -4,4'-diphenylmethane diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate and any Mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diisocyanate, 3,2'- and / or 3,4-diisocyanato-4-methyl-diphenylmethane, Naphthylene-1,5-diisocyanate, triphenyl-methane-4,4'-4 "-triisocyanate, polyphenylpolymethylene polyisocyanate, as obtained by aniline-formaldehyde condensation and subsequent phosgenation and e.g. in GB-PS 874 4 30

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and 848,671. In addition to these simple polyisocyanates, there are also heteroatoms in the, the Polyisocyanates containing radicals linking isocyanate groups suitable. Examples of these are polyisocyanate containing carbodiimide groups, as described in DE-PS 1 092 007, polyisocyanates containing allophanate groups, such as those described, for example, in GB-PS 994 890, BE-PS 761 626 are described, polyisocyanates containing isocyanurate groups, as described, for example, in US Pat. No. 4,288,586, in DE-PS 1 022 789, 1 222 067 and 1 027 394, in DE-OS 1 929 034, 2 004 048 and 2 839 133 or in EP-PS 10 589, containing urethane groups Polyisocyanates as described, for example, in BE-PS 752 261 or in US-PS 3,394,164 are polyisocyanates containing acylated urea groups According to DE-PS 1 230 778, polyisocyanates containing biuret groups, such as those described, for example, in US Pat DE-PS 1 101 394, in GB-PS 889 050 and in

20 FR-PS 7 017 514 are described.

Particularly suitable for the process according to the invention Polyisocyanates are the "paint polyisocyanates" known per se, i.e. biuret, isocyanurate or Modification products containing urethane groups of the abovementioned simple polyisocyanates, in particular tris (6-isocyanatohexyl) biuret, if appropriate in a mixture with its higher homologues, by trimerization of aliphatic and / or aromatic Diisocyanates such as hexamethylene diisocyanate,

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Isophorone diisocyanate, diisocyanatotoluene or Geraischen polyisocyanates containing isocyanurate groups obtainable from diisocyanatotoluene and hexamethylene diisocyanate, above all, the tris (6-isocyanatohexyl) isocyanurate, which may be present in a mixture with its higher homologues or low molecular weight polyisocyanates containing urethane groups, such as those made by, for example Implementation of excess amounts of 2,4-diisocyanatotoluene with simple polyhydric alcohols of the molecular weight range 62-300, especially with trimethylolpropane and subsequent removal by distillation of the unreacted excess diisocyanate can be obtained. Of course you can too any mixtures of the exemplified poly-

15 isocyanates can be used to produce the products according to the invention.

Polyisocyanates which are also well suited for the process according to the invention are the known, terminal polyisocyanates Prepolymers containing isocyanate groups, such as are obtained, in particular, by reaction of the abovementioned simple polyisocyanates, especially diisocyanates with insufficient amounts of organic Compounds with at least two isocyanate-reactive groups are accessible. as such are in particular a total of at least two amino groups, thiol groups, carboxyl groups and / or Compounds containing hydroxyl groups in the molecular weight range from 300 to 10,000, preferably 400 to 6000 are used. Preference is given to the

30 speaking polyhydroxyl compounds are used.

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Hydroxy compounds that are preferably to be used are the hydroxypolyesters known per se in polyurethane chemistry, Hydroxypolyethers, Hydroxypolythioether, Hydroxypolyacetals, Hydroxypolycarbonate and / or Hydroxy polyester amides.

Representatives of the named to be used for the preparation of the NCO prepolymers suitable according to the invention Polyisocyanate and hydroxyl compounds are described, for example, in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology ", written by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, Pages 32-42 and pages 44-54 and Volume II, 1964, pages 5-6 and 198-199, as well as in the Kunststoff-Handbuch, Volume VII, Vieweg-Höchtlen, Carl-Hanser-Verlag, Munich,

15 1966, e.g. on pages 45 to 71.

In the production of the NCO prepolymers by per se known principles of the prior art, the reactants are generally in such proportions used, which has a ratio of isocyanate groups to hydrogen atoms reactive towards NCO, preferably from hydroxyl groups, from 1.05 to 10, preferably from 1.1 to 3, correspond.

The type and proportions of the starting materials used in the production of the NCO prepolymers are also preferably chosen so that the NCO prepolymers

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- χί -

a) an average NCO functionality of 2 to 4, preferably from 2 to 3 /

b) an average one, based on the stoichiometry of the starting materials calculable molecular weight from 500 to 10,000, preferably from 800 to 4000 exhibit.

Reactants for the organic polyisocyanates mentioned by way of example are in the case of the invention Process any organic compound that has a structural unit of the formula

• C-0

and, apart from this grouping, are inert towards isocyanate groups. Such cyclic Dicarbonyl compounds are predominantly in the diketo form represented by the formula given and only to a very small fraction in that

Enol form

OH

C-O.

CH

C-O

ti

0
before. In the context of the present disclosure of the invention, the diketo form is therefore representative for

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the mixture of the two tautomeric forms. All quantities relate, if the respective compounds occur partially in the enol form, on the mixture of both tautomers.

Suitable cyclic dicarbonyl compounds of this type are those of the formula

.C-O.

Il

for which

R and R ^{1 represent} identical or different radicals and optionally denote alkyl or aryl groups having inert substituents or, together with the carbon atom linked to the two oxygen atoms, form a cycloalkyl ring optionally having inert substituents.

Those compounds of the general formula mentioned last are particularly suitable for which

R and R ^{1 represent} identical or different radicals and represent alkyl radicals having 1 to 4 carbon atoms, in particular methyl radicals

or in which the radicals R and R ¹ together with the carbon atom linked to the oxygen atoms form a cycloaliphatic ring with 5 to 6, in particular

25 form 6 carbon atoms.

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-μ -

The best-known representative of this product class is particularly preferred, isopropylidene malonate, also known as Meldrum's acid (R = R ¹ = CH). The compound can be obtained by condensation of malonic acid with acetone under acidic catalysis (cf. AN Meldrum, J. Chem. Soc. JH) ./ 598 (1908); D. Davidson et al., J. Amer. Chem. Soc. 1Q_, 3429 (1948)). Correspondingly, the other cyclic dicarbonyl compounds suitable according to the invention can be prepared by condensation from malonic acid and ketones of the formula

ο.

produced v / earth, where

R and R ^{1 have} the meaning or preferred meaning already mentioned above.

for example, methyl ethyl ketone, methyl isobutyl ketone, Cyclopentanone, cyclohexanone or acetophenone are suitable reactants for the malonic acid in the preparation of the cyclic dicarbonyl compounds suitable according to the invention as blocking agents

20 fertilize.

Appropriate synthesis methods are described, for example, by B. Eistert et al., In Chem. Ber. 94, 929 (1961); by J. Swoboda et al. in monthly 9JL, 188 (196 0) or by A. Michael et al, in J. Amer. Chem. Soc. 58, 680 (1936).

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For the preparation of the blocked polyisocyanates according to the invention the components described in detail above / i.e. the organic polyisocyanates and the cyclic dicarbonyl compounds reacted with one another. The invention cyclic dicarbonyl compounds are used in amounts which are at least 10 equivalent%, based on the NCO groups correspond to the polyisocyanates. This means that the reactants in the implementation of the invention Process in, a molar ratio of cyclic dicarbonyl compounds to isocyanate groups of the starting polyisocyanate of at least 0/1: 1 corresponding amounts are used. Preferably such amounts of cyclic dicarbonyl compounds are used that 30-100% of the isocyanate groups react with it, i.e. the starting materials preferably come in a molar ratio of cyclic dicarbonyl compounds to isocyanate groups of the starting polyisocyanate of 0.3: 1 up to 1: 1 corresponding amounts are used. Basically However, it is also possible to speed up and complete the implementation even excess Use amounts of cyclic dicarbonyI compound. In general, however, such an excess becomes 10 to 20 equivalent% based on the isocyanate groups of the starting polyisocyanate.

In the event that the cyclic dicarbonyl compounds in molar deficit compared to the NCO groups of Polyisocyanates are used, one can preferentially

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wise react the excess isocyanate groups with other monofunctional blocking agents. Any isocyanate blocking agents, as described, for example, by ZW Wicks, Jr., Progress in Organic Coatings % 3-28 (1981), are suitable for this purpose. Examples of such blocking agents to be used are: CH-acidic compounds such as dialkyl flalonate and alkyl acetoacetate, oximes such as acetone oxime, methyl ethyl ketone oxine and acetaldoxime, lactams such as ο -caprolactam, phenols such as phenol itself or its alkyl derivatives. Such blocking agents are used in the process according to the invention, if at all, in a maximum amount corresponding to a molar ratio of blocking agent to isocyanate groups of the starting polyisocyanate of 0.9: 1.

However, it is also readily possible to have the cyclic dicarbonyl compounds in a deficit in molar terms to use the NCO groups of the polyisocyanates and to free the NCO groups remaining after the reaction leave, so that these are active for further reactions, e.g. with chain extenders, water or Zerewitinow Hydrogen atom-bearing polymers are available.

The reaction between the cyclic dicarbonyl compounds useful in this invention and the polyisocyanates is generally carried out at temperatures of 0 ⁰ C to 80 ⁰ C, preferably from 20 ⁰ C to 6O ⁰ C. If, as described, some of the isocyanate groups are to be reacted with other blocking agents, the reaction with these blocking agents can take place before or after the reaction with the cyclic dicarbonyl compound or at the same time as it.

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To accelerate the reaction, bases, preferably organic bases, can be used in a manner known per se, tertiary amines are particularly preferably used. As detailed below, these bases become preferably used in an amount of 50-100 mol%, based on the amount of cyclic dicarbony compounds. This results in blocked polyisocyanates, which have the advantage according to the invention, directly, i.e. to be soluble or dispersible in water without further modification. The reaction is preferred carried out in an organic solvent, although in principle, e.g. when used especially low-viscosity polyisocyanates, is also possible without solvents. Suitable solvents are e.g. ethylene glycol ethyl ether acetate, Propylene glycol methyl ether acetate, butyl acetate, acetone, methyl ethyl ketone, cyclohexanone, Ν, Ν-dimethylformamide and N-methyl! Pyrrolidone.

Organic solvents which are also water-soluble are preferably used. This enables a particularly easy dispersion of the products in the event that the blocked polyisocyanates are in the form aqueous solutions or dispersions are to be used. Particularly preferred as such a solvent is N-methylpyrrolidone. The organic solvents are generally used in an amount of 5-50%, preferably 10-30%, based on the total mixture.

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As already mentioned, the products of the process according to the invention have the interesting property of being soluble or dispersible in water in the presence of bases to be. Bases suitable for this purpose are, in particular, any tertiary amines, i.e. any organic compounds, the at least one tert. Have nitrogen atom, and which preferably have a molecular weight from 5 9 to 3 00. Monovalent tert. Amines are preferred. Suitable tert. Amines are e.g. trimethylamine, Triethylamine, N, N-dimethylbenzylamine or. N, N-dimethylethanolamine.

The type of interaction of the polyisocyanates blocked according to the invention with the amines is not precisely known, Presumably, this surprising phenomenon is due to the fact that the invention with cyclic Dicarbonyl compounds blocked isocyanate groups have acidic hydrogen atoms, i.e. monobasic Represent acids that are capable of forming ammonium salts with the amines. In general is the solubility or dispersibility of the products of the process according to the invention is given when they . a content of "neutralized" isocyanate groups blocked with cyclic dicarbonyl compounds of at least 80, preferably 110 to 300 milliequivalents per 100 g of solids, including the amines. The particle size of the dissolved or dissolved in the aqueous phase dispersed solid depends primarily on the content of such ionic structural units.

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As mentioned above, these bases are preferably already added in the preparation of the blocked polyisocyanates according to the invention, at the same time as Catalysts work. When base-free or low-base blocked polyisocyanates of the type mentioned in water are to be dispersed, it is possible, however, to add the bases only immediately before or during the dispersion, e.g. by adding the bases to the dispersing water. The dispersion of the invention

10 products can be entered in the

aqueous phase and vice versa by stirring in the aqueous phase into the solution or melt of the blocked polyisocyanates or by continuous mixing of the two phases take place in suitable mixing units.

Is e.g. for reasons of viscosity the use of organic solvents in the dissolution or dispersion of the products necessary and should nevertheless be solvent-free aqueous dispersions or solutions of the blocked If polyisocyanates are obtained, the solvent can be used in a known manner with a sufficiently low solvent Choose a boiling point, such as acetone, that can be distilled off after dispersion. One used for the dispersion is generally so much water that the dispersions have as high a solids content as possible exhibit. As a rule, solutions or dispersions with 30-60% solids can be produced very well.

For the preparation of aqueous solutions or dispersions of the process products according to the invention, preference is given to selected those that do not contain any free isocyanate

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have more groups, i.e. their isocyanate groups completely with essential to the invention and optionally the "classic" blocking agents mentioned by way of example are blocked. Basically it would be however, it is also conceivable to use aqueous solutions or dispersions of free isocyanate groups according to the invention To produce process products, which of course implies a destruction of these free isocyanate groups run out with chain extension with urea formation would.

The products of the process according to the invention are suitable especially as a reactant for compounds with isocyanate-reactive hydrogen atoms in the production of high molecular weight isocyanate polyaddition products. For this purpose as a reactant for the process products according to the invention suitable reactants are those known from polyurethane chemistry, at least two opposite Compounds containing isocyanate groups and having reactive groups and having a molecular weight range of 60 to 10,000, preferably 400 to 6000. These are in particular at least two alcoholic Compounds containing hydroxyl groups, carboxyl groups, amino groups and / or thiol groups. The corresponding Polyhydroxy compounds are the preferred reactants for the products of the process according to the invention. Examples are the known ones

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--2TT -

Polyhydroxy polyester, polyether, polythioether, -polyacetals, -polycarbonates or -polyesteramides, as they are in the literature references already cited above "High Polymers" or "Plastics Handbook" are mentioned by way of example. The known polyhydroxypolyacrylates are also very suitable reaction partners or oligourethanes having at least two hydroxyl groups in the above molecular weight range, as they are obtained by reacting excess amounts of polyhydroxy compounds with polyisocyanates of the above exemplified type are accessible. Also epoxy resins of the glycidyl ether type, such as those for example obtainable by reacting bisphenol A with excess amounts of epichlorohydrin are suitable Reaction partner for the products of the process according to the invention. Particularly preferred reactants for the products of the process according to the invention are the polyhydroxy polyesters and polyethers mentioned by way of example, polyacrylates and oligourethanes as well as the low molecular weight known per se from polyurethane chemistry, Chain extenders or crosslinkers of the molecular weight range containing at least two hydroxyl groups 62 - 300 such as ethylene glycol, tetramethylene glycol, 1,2-butanediol, hexamethylene glycol, Glycerine or trimethylol propane. Of course, any mixtures of such compounds can be used groups which are reactive toward isocyanate groups in the use according to the invention of the groups according to the invention Process products for the production of isocyanate polyaddition products, in particular polyurethanes are used.

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- ΥΣ -

In this inventive use of the process products according to the invention, the reactants are in, an equivalent ratio of blocked isocyanate groups to isocyanate-reactive groups of 0.1: 1 to 1: 1.2, preferably 0.3: 1 to 1: 1 and, an equivalent ratio from free and blocked isocyanate groups to isocyanate-reactive groups of 0.8: 1 to 1: 1.2, preferably 1: 1, corresponding amounts mixed with one another, the free isocyanate groups which may be present with some of the isocyanate-reactive groups spontaneously to form oligomeric groups plastic precursor reacted during the reaction between blocked isocyanate groups and the isocyanate-reactive groups takes place only under the influence of heat, for example in the temperature range of 80-250 ⁰ C, preferably from 100 to 180 ⁰ C. The reactants can be mixed in the presence of organic solvents of the type already mentioned above by way of example. Such solutions can be used, for example, as heat-crosslinkable clear lacquers or for the production of pigmented lacquers.

Another possible use of the products of the process according to the invention is the production of aqueous stoving enamels, aqueous solutions or dispersions of compounds with opposite isocyanate groups reactive groups with water-soluble or water-dispersible process products according to the invention of the above type can be combined.

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- «2Γ3 -

For this purpose, too, such process products according to the invention are preferably used in accordance with the statements made above used, which have only blocked isocyanate groups, preferably here Equivalent ratio of blocked isocyanate groups to isocyanate-reactive groups is 0.1: 1 to 1: 1.2, preferably 0.8: 1 to 1: 1.1. The preparation of such aqueous solutions or dispersions can easily be done in such a way that the water-soluble or dispersible according to the invention Process products with previously prepared aqueous solutions or dispersions of the active hydrogen containing Compounds mixed. It is also possible, as described above, to initially use an aqueous solution or to produce a dispersion of the products of the process according to the invention and then to produce them separately aqueous solutions or dispersions of the compounds with isocyanate-reactive groups Mix groups. In both cases it is of course necessary that the connections with isocyanate-reactive groups if they are not water-soluble or dispersible e.g. with the help of external emulsifiers or preferably by incorporating hydrophilic groups such as carboxylate or sulfonate groups so that the compounds are soluble in water or are dispersible. Particularly suitable compounds of this type are carboxyl and hydroxyl groups containing polyacrylates or oligourethanes of the above molecular weight range, whose carboxyl

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groups for example with tert. Amines of the type exemplified above into hydrophilic carboxylate groups are transferable.

In principle, it is also conceivable to use the unneutralized Process products according to the invention with aqueous solutions of organic polyamines, in particular diamines with primary or secondary amino groups such as ethylenediamine, diethylenetriamine, hexamethylenediamine or isophoronediamine to mix, the primary or secondary amino groups having the dual function of a neutralizing agent for the isocyanate groups blocked according to the invention while ensuring their solubility in water or dispersibility and a reactant for the blocked and free isocyanate groups of process products according to the invention take over, so that also aqueous solutions or dispersions of crosslinkable under the influence of heat Systems arise. This use of the process products according to the invention is conceivable in principle

20 less preferred, however.

The combinations of process products according to the invention and compounds with opposite isocyanate groups reactive groups are both in the form of organic solutions and in the form of aqueous dispersions or solutions stable to gelation and coagulation at room temperature even after prolonged storage or sedimentation. They are extremely suitable for the production of plastics, in particular

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C7

-2S-

of coatings and sealing compounds on a variety of substrates such as textiles, leather, glass fibers, Plastics, ceramic materials, glass and wood. The combinations are particularly suitable but as stoving enamels for heat-resistant substrates, especially for metals.

To produce the coatings, the substrates are coated with the combinations according to the invention, which may optionally be mixed with the auxiliaries customary in paint technology, such as pigments, fillers or leveling aids, by customary methods, for example by spraying, brushing or dipping. The thermal cure is generally carried out in the temperature range of 80-250 ⁰ C, preferably from 100 to 18O ⁰ C, the removal of any solvents or water by evaporation or vaporization before or during this heat treatment takes place.

The following examples serve to further illustrate the invention. All percentages relate unless otherwise stated, to percentages by weight.

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- • 2t -

example 1

In a mixture of 400 g of an isocyanurate polyisocyanate obtained by trimerization of hexamethylene diisocyanate (NCO content 21%), 300 g of isopropylidene malonate (Meldrum's acid) and 300 g of N-methylpyrrolidone, 088 g of triethylamine is added dropwise with stirring. The mixture is subsequently stirred at 50 ^° C. for 8 hours until NCO groups can no longer be detected by IR spectroscopy. The product has a viscosity of 20,000 mPas (23 ° C.), a blocked NCO group content of 7.0%, a neutralized blocked isocyanate group content of 229 million equivalents per 100 g and has good water solubility.

Example 2

from 60 g of the blocked polyisocyanate according to Example 1 and 50 g of a 75% solution of an OH-functional Lacquer polyester in ethyl glycol acetate ("polyester resin A", made from 29.6% isophthalic acid; 10.1% adipic acid; 5.9% o-phthalic acid, 42.4% 1,6-hexanediol; 12.0% trimethylol propane; OH number 150) a clear lacquer is produced. The equivalent ratio between blocked isocyanate groups and Hydroxyl groups is 1: 1.

The paint is applied on a glass plate (wet film thickness: 120 μΐη) and 3 0 min at 14O ⁰ C baked. An elastic paint film with a dry surface and good solvent resistance is obtained (see Table 1).

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33261

- yt -

Example 3

60 g of the blocked polyisocyanate according to Example 1
become 263 g of a 30% strength with thorough stirring
given aqueous dispersion of an OH-functional polyurethane resin. The dispersion of this resin ("polyurethane resin B") was prepared from the following starting materials; 15.0% polyester diol from neopentyl glycol
and hexahydrophthalic acid, OH number 192; 3.2% polyester diol from 1,6-hexanediol and adipic acid, OH number 133;

0.77% trimethylol propane; 2.56% dimethylol propionic acid; 8.47% isophorone diisocyanate; 2.6% dimethylbenzylamine; 0.4% triethylamine; 67.0% water. The OH number of the
OH-functional polyurethane resin, based on solids, without amines, is 71.2. The equivalent ratio of blocked isocyanate groups to hydroxyl groups in the resin is 1: 1.

The blocked isocyanate dissolves smoothly and completely. A finely divided and storage-stable aqueous stoving enamel dispersion is formed. This will
on glass plates coated (wet film thickness: 120 pm) and 30 min baked at 140 ⁰ C and 160 ⁰ C. You get
elastic paint films with dry surface and
good solvent resistance (see Table 1).

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Tabel

Paint film properties

Example 2

Polyester resin A

Example 3

Stoving temperature surface ¹ * elasticity (span)

2)

Resistance to solvents (cotton ball, 1 min / 5 min) Toluene EthyIglykolacetat acetone

140 ⁰ C

1/4 1/4 4

140 ⁰ C

5 5 5

14O ⁰ C

2-3

Polyurethane resin B

16O ⁰ C

2-3

160 ⁰ C

0/1 0/0 3/5 0/1 0/0 5 4th 4th 5

Explanations

1) 0 = dry 5 = sticky

2) 0 = very soft 2 = elastic 5 = very brittle

3) 0 = paint unchanged 3 = swollen 5 = dissolved.

The solvent resistance was tested by placing a with the
Solvent-soaked cotton ball. Specifying only one number means that
the cotton ball was placed on for a period of 1 minute. When specifying
two numbers, the first number refers to a 1 minute and the second number
on a 5-minute application of the cotton ball.

Example 4

2.5 g of sodium phenolate are added to a mixture of 40O g of an isocyanurate polyisocyanate obtained by trimerizing hexamethylene diisocyanate (NCO content: 21%), 128 g of diethyl malonate and 300 g of N-methylpyrrolidone. The mixture is stirred at 60 ^° C. until the calculated content of free NCO groups is just below 6%. After cooling to 30 ^° C., 173 g of isopropylidene malonate and then 121 g of triethylamine are added dropwise. After the exothermic reaction for 8 hours at 5O ⁰ C is stirred until IR spectroscopy NCO groups were no longer detectable. The product has a viscosity of 11 000 mPas (23 ⁰ C), a content of blocked NCO groups of 7.5%, a content of the neutralized isopropylidene-blocked isocyanate groups of 146 milliequivalents per 100 g and has a good water solubility.

Example 5

A clear lacquer is produced from 56 g of the blocked polyisocyanate according to Example 4 and 50 g of a 75% strength ethyl glycol acetate solution of the polyester resin A described in Example 2. It is applied on a glass plate (wet film thickness: 120 μπι) and 30 min at 140 ⁰ C baked. The equivalent ratio between blocked isocyanate groups and hydroxyl groups is 1: 1. An elastic paint film with a dry surface and good solvent resistance is obtained (see Table 2).

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Example 6

56 g of the blocked polyisocyanate according to Example 4 are added to 263 g of a 30% strength aqueous dispersion of the polyurethane resin B described in Example 3 with thorough stirring. The blocked polyisocyanate dissolves smoothly and completely. The equivalent ratio of blocked isocyanate groups to hydroxyl groups is 1: 1. The result is a finely divided and storage-stable aqueous stoving lacquer dispersion on glass plates coated (wet film thickness: 120 pm), and is baked for 30 minutes at 14O ⁰ C and 16O ⁰ C. Elastic paint films with a dry surface and good solvent resistance are obtained (see Table 2).

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tr * table 2

(D

Paint film properties

Example 5

Polyester resin A

Example 6

Polyurethane resin B

2)

Baking temperature surface ¹⁾ Elasticity (span) Resistance to solvents (cotton ball, 1 min / 5 min) Toluene

Ethyl glycol acetate acetone

140 ⁰ C

0/2

14O ⁰ C

5
5
5

140 ⁰ C

2-3

16O ⁰ C

2-3

16O ⁰ C 0

0/4 0/2 3/5 2/4 0/4 5 4th 4th 5

Explanations: see table

OO NJ CD

Example 7

70 g of butanone oxime are added dropwise to a mixture of 372 g of a polyisocyanate containing biuret groups and based on hexamethylene diisocyanate (NCO content: 22.6%) and 300 g of N-methyl pyrrolidone. The mixture is stirred for 3 hours at 5 0 ⁰ C, cooled to 30 ⁰ C. and 173 g of isopropylidene to. 121 g of triethylamine are then added dropwise. After the exothermic reaction has subsided, stirring is continued for 8 hours at 50 ^° C. until NCO groups can no longer be detected by IR spectroscopy. The product obtained has a viscosity of 6000 mPas (23 ⁰ C), a content of blocked NCO groups of 8.1%, a content of the neutralized isopropylidene-blocked isocyanate groups of 163 flilliäquivalenten per 100 g, and is water soluble.

An analog to Example 2 from this blocked polyisocyanate and the polyester resin A paint prepared (blocked NCO: OH = 1) is dry when baked (30 min / 14O ⁰ C), elastic and shows good water and solvent resistance.

Example 8

A mixture of 400 g of a by trimerization of hexamethylene diisocyanate isocyanurate polyisocyanate obtained (NCO content 21%), 300 g N-methylpyrrolidone and 90.4 g £ -caprolactam is stirred at 6O ⁰ C until

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the calculated NCO content is just below 6.4%. 173 g of isopropylidene malonate are added to this solution. 121 g of triethylamine are then added dropwise. After the exothermic reaction has subsided, stirring is continued for 8 hours at 50 ^° C. until NCO groups can no longer be detected by IR spectroscopy. The product has a viscosity of 8500 mPas (23 ⁰ C), a content of blocked NCO groups of 7.7%, a content of the neutralized isopropylidene-blocked isocyanate groups of 153 million! Equivalent per 100 g and has good water solubility.

A varnish produced analogously to Example 2 from this blocked polyisocyanate and polyester resin A. (blocked NCO: OH = 1) is after stoving

(30 min / 160 ⁰ C) dry, elastic and shows good water and solvent resistance.

Example 9

To a mixture of 100 g of an isocyanurate polyisocyanate (NCO content: 21%) obtained by trimerization of hexamethylene diisocyanate, 92 g of cyclohexylidene malonate and 75 g of N-methylpyrrolidone, 50 g of triethylamine are added dropwise. Stirring is continued for 8 hours at 5 0 ^° C. until NCO groups can no longer be detected by IR spectroscopy. The product has a viscosity of 150,000 mPas (23 ° C.) and a blocked NCO content

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of 6.6%, a content of neutralized cyclohexylidene ralonate-blocked Isocyanate groups of 208 milliequivalents per 100 g and is water soluble.

A analogously to Example 2 from this blocked polyisocyanate and the polyester resin paint prepared Ά (blocked NCO: OH = 1) is elastically when baked (30 min / 140 ⁰ C), tack-free and water and solvent resistant.

Example 10

A blocked polyisocyanate is prepared as described in Example 9, with the difference that 85 g of cyclopentylidene malonate are used instead of the cyclohexylidene malonate. The product obtained has a viscosity of 135 000 mPas (23 ⁰ C), a blocked NCO content of 6.8% and is water soluble. A paint produced analogously to Example 9 shows comparable properties.

' Example 11

A solution of 134 g of trimethylolpropane in 437 g of N-ilethylpyrrolidone is added dropwise to 522 g of diisocyanatotoluene (isomer mixture 2.4: 2.6 = 80:20) with cooling. After the exothermic reaction the mixture at 6O ⁰ C is stirred, is just below until the calculated NCO content of 11.5%.

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300 g of this adduct are initially introduced at room temperature and 40 g of N-methylpyrrolidone and 116 g of isopropylidene malonate are added. 81 g of triethylamine are slowly added to this mixture and the mixture is subsequently stirred at 50 ^° C. for 4 hours until NCO groups can no longer be detected by IR spectroscopy. Then 500 g of water are added. A clear, yellowish solution is formed, to which 135 g of 6 N HCl are added dropwise. The base-free blocked isocyanate precipitates out in the form of a light-colored precipitate. This is filtered off, washed with water and dried in vacuo.

Yield: 284 g (96% of theory)

Pale yellow powder, melting point: 92-95 ⁰ C

Example 12

37 g of the solid blocked polyisocyanate according to Example 11 are introduced into a mixture of 76 g of water and 10.1 g of triethylamine with stirring. The result is a finely divided, storage-stable aqueous dispersion which is free from organic cosolvents. The dispersed solid has a content of neutralized isopropylidene malonate-blocked isocyanate groups of 212 milliequivalents per 100 g. By mixing with 263 g of the 30% strength aqueous dispersion of the polyurethane resin B described in Example 3, an aqueous stoving lacquer is obtained from which lacquer films which are dry and solvent-resistant ^{after 30 min / 140 ° C. can be obtained.}

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Example 13

0.2 g of triethylamine are added to a solution of 57.6 g of isopropylidene malonate, 50 g of 4,4'-isocyanatodiphenylmethane and 200 g of N-methylpyrrolidone. The mixture is ^{stirred at 40 °} C. for 35 hours. Thereafter, NCO groups can no longer be detected by IR spectroscopy. 150 g of water are added and the mixture is stirred while cooling
35 g of 6N HCl. The resulting precipitate is filtered off, washed with cold water and dried in vacuo.

Yield: 82 g of solid blocked diisocyanate (78% of theory). Content of blocked NCO groups: 15.5%.

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Claims (9)

Claims /Τ.Ϊ Process for the preparation of organic polyisocyanates with at least partially blocked isocyanate groups by at least partially blocking the isocyanate groups of organic polyisocyanates with blocking agents for isocyanate groups / characterized in that the blocking agent a) the characteristic structural unit containing, cyclic dicarbonyl compounds and optionally additionally b) blocking agents known from polyurethane chemistry used, wherein the blocking agent a) in, a molar ratio of blocking agent a) to Isocyanate groups of the starting polyisocyanate of at least 0.1: 1 corresponding amounts are used arrives, 'and where, in the case of the use of blocking agents b), these before, simultaneously with or after the implementation of the Le A 22 439 -JtS- Starting polyisocyanate with the blocking agent a) brought to reaction with the starting polyisocyanate will. 2. The method according to claim 1, characterized in that the blocking agent is a) compounds of the formula used, where R and R ¹ stand for identical or different radicals and optionally inert substituents tuenten having alkyl or aryl groups or together with the optionally one carbon atom linked to the two oxygen atoms inert substituents having cyclo- form an alkyl ring. 3. Process according to Claims 1 and 2, characterized in that the blocking agent a) those of the formula mentioned in claim 2 are used, where R and R ¹ each represent methyl radicals or together with the, with the two acidic Le A 22 43 9 material atoms linked carbon atom form a cyclohexane or cyclopentane ring form. 4. The method according to claim 1 to 3, characterized in that that the blocking agent b) dialkyl malonate, alkyl acetoacetate, Ketoximes, aldoximes, lactams, optionally alkyl-substituted Phenols or mixtures of such blocking agents are used, the blocking agent b) in, a ratio of blocking agent to isocyanate groups of the starting polyisocyanate of a maximum of 0.9: 1 corresponding amounts are used. 5. The method according to claim 1 to 3, characterized in that only blocking agents of the type mentioned under a) are used in a molar ratio of blocking agents to isocyanate groups of the starting polyisocyanate from 0.3: 1 to 1: 1 corresponding amounts are used. 6. According to claim 1 to 5 obtainable polyisocyanates with at least partially blocked isocyanate groups . 7. Use of the according to claim 1 to 5 obtainable Polyisocyanates with at least partially blocked isocyanate groups as reactants for organic Polyhydroxy compounds in the production of Polyurethane plastics, especially paints, Le A 22 43 9 layering or sealing compounds based on polyurethane. 8. Use of the polyisocyanates obtainable according to claims 1 to 5 with at least partially blocked ones Isocyanate groups for the production of aqueous stoving enamels, characterized in that the Polyisocyanates with aqueous solutions or dispersions of organic compounds with at least two isocyanate-reactive groups in the presence of one, the solubility or The amount of a base ensuring the dispersibility of the polyisocyanates in water is adhered to an equivalent ratio of blocked isocyanate groups to opposite isocyanate groups reactive groups from 0.1: 1 to 1: 1.2, optionally with the use of in the Mixing of conventional auxiliaries and additives in paint technology. 9. Use of the polyisocyanates obtainable according to claims 1 to 5 with at least partially blocked ones Isocyanate groups for the preparation of aqueous polyisocyanate solutions or dispersions, characterized in that the polyisocyanates are in the presence an amount which ensures the solubility or dispersibility of the polyisocyanates Base mixed with water. Le A 22 439